Deep organ access device and method

ABSTRACT

Devices and methods provide accurate targeting, placement, and/or stabilization of an electrode or other instrument(s) into the brain or other body organ, such as to treat severe tremor or other neurological disorders. Targeting is performed using any form of image-guidance, including real-time MRI, CT, or frameless surgical navigation systems.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation application of Ser. No.09/828,451, filed Apr. 6, 2001, entitled: DEEP ORGAN ACCESS DEVICE ANDMETHOD.

[0002] This patent application claims the benefit of priority, under 35U.S.C. Section 119(e), to U.S. Provisional Patent Application Ser. No.60/195,663, filed Apr. 7, 2000, the disclosure of which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

[0003] This document relates generally to, among other things, surgicalplacement of a medical instrument deeply into an organ, such as a brain,and specifically, but not by way of limitation, to accurate targeting,placement, and/or acute or chronic stabilization of such an instrument.

BACKGROUND

[0004] In placing a medical device or instrument deeply into an organ,such as a brain, it is often advantageous to precisely target, place,and then secure the device for a period of time that may be several daysor even indefinitely. Examples of such devices include catheters,needles, and drug and biological agent delivery instruments, as well aselectrical mapping, stimulating and/or ablation leads.

[0005] Targeting such a device is not always an exact science. Thetarget is not always visible from preoperative images. Even when usingimage-guided minimally invasive techniques, with such imaging modalitiesmagnetic resonance imaging (MRI), computed tomography (CT), framelesssurgical navigation systems, and the like, there is often a need forsome tweaking or small adjustment in trajectory to accurately hit thetarget. A single trajectory approach would mean that the need to movethe target slightly laterally would require removing the device and thenreintroducing it, sometimes as close as 2 mm away from the originalentry site.

[0006] One approach to positioning an instrument, such as a deep brainstimulation electrode, uses a conventional stereotactic frame systemthat is secured to the patient. In this approach, preoperative images ofthe patient are used to determine the proper trajectory to the target,as measured and aligned relative to the frame. Using accessories mountedto the frame, the electrode is aligned and advanced through a burr holein the skull to the predetermined target. A base is then inserted intoand/or around the burr hole. Various “tool holes” and slots in the baseare deformed as the base is slid over the electrode. The tool holes inthe base are squeezed together as the base is inserted into the burrhole. When the base is released, it springs back outward against theinside diameter of the burr hole. The stereotactic accessories must thenbe carefully removed while holding the device in place. This step can beclumsy and inexact. If the electrode moves, it must be repositioned.Before securing the carefully-positioned device to the patient, theequipment used to introduce the device and maintain trajectory must beremoved. This action can often dislodge the device requiring the entireplacement procedure to be repeated. Even after the stereotacticaccessories have been removed, the electrode or other device must besecured. This procedure may also cause electrode movement. In oneexample, a silicone rubber cap is fit into place to capture and protectthe electrode. Placing the rubber cap may cause further electrodemovement.

[0007] One disadvantage of this approach is that the instrumentpositioning is attempted using only a presumed target location, based onthe preoperative images, and not an actual determination of the neededtrajectory to the target. Another disadvantage is that the stereotacticframe system is both expensive and unwieldy. Yet another disadvantage isthat the electrode may move at any one of several times during theprocedure and therefore require repositioning. For these and otherreasons, the present inventors have recognized that there is a need forimproved targeting, placement, and secure stabilization of a deep brainelectrode or other medical instrument.

SUMMARY

[0008] This document discusses, among other things a device and methodfor instrument targeting, placement, and/or stabilization. This systemmay be used with any instrument, but it is particularly useful with adeep brain neurological stimulation electrode to treat severe tremor orother disorders. The system allows any of a number of imagingmodalities, including MRI, CT, and frameless surgical navigation. TheMRI environment typically provides both real-time brain images andreal-time MRI imaging of trajectory-alignment fiducial markings,although preoperative MRI images of the brain could also be used. Theframeless surgical navigation typically uses retrospective brain images(e.g., previously-acquired preoperative MRI images of the brain) andreal-time imaging recognition of trajectory-alignment fiducial markings(e.g., using light-emitting diodes, reflective globes, etc.). Bothenvironments, therefore, provide image-guided alignment of theinstrument's trajectory to the target location. Such techniques provideaccurate placement of the electrode or other medical instrument. It alsoprovides acute and/or chronic stabilization of the instrument. Thesystem includes, among other things, an alignment/targeting system, aninstrument introducer system, and a stabilizer system. Other aspects ofthe present system and methods will become apparent upon reading thefollowing detailed description of the invention and viewing the drawingsthat form a part thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the drawings, which are not necessarily drawn to scale, likenumerals describe substantially similar components throughout theseveral views. Like numerals having different letter suffixes representdifferent instances of substantially similar components. The drawingsillustrate generally, by way of example, but not by way of limitation,various embodiments discussed in the present document.

[0010]FIG. 1 is a cross-sectional view example of an electrode that hasbeen implanted and secured using the devices and methods discussedherein.

[0011]FIG. 2 is a perspective view example of a base and a cap.

[0012]FIG. 3 is an exploded perspective view example of an assembly of abase, a stabilizer, and a cap.

[0013]FIG. 4 is a perspective view example of a stabilizer.

[0014]FIG. 5 is an exploded perspective view example of a base, astabilizer, and a cap.

[0015]FIG. 6 provides two perspective view examples of a base and aburr-hole centering device.

[0016]FIG. 7 is a perspective view example of a tool for placing thestabilizer, securing the introduced instrument, and removing the cap.

[0017]FIG. 8 is a perspective view example of an instrument-securingbase and a equipment-supporting base.

[0018]FIG. 9 is another perspective view example of aninstrument-securing base and an equipment-supporting base.

[0019]FIG. 10 is a further perspective view example of aninstrument-securing base and an equipment-supporting base.

[0020]FIGS. 11 and 12 are perspective view examples of a tower-likeinstrument alignment and introduction guide assembly, also referred toas a deep brain access device.

[0021]FIG. 13 is an exploded perspective view example of portions of adeep brain access device.

[0022]FIG. 14 is a perspective view example of adjusting an instrumenttrajectory using portions of a deep brain access device with MRI, CT, oranother imaging modality.

[0023]FIG. 15 is a perspective view example of adjusting an instrumenttrajectory using portions of a deep brain access device with a framelesssurgical navigational system.

[0024]FIG. 16 is a perspective view example of an MRI-imagable alignmentstem.

[0025]FIG. 17 is a perspective view example of an adapter for receivinga frameless surgical navigation instrument.

[0026]FIG. 18 is a perspective view example of a technique forintroducing an instrument along the previously established trajectoryusing a peel-away sheath and stylet.

[0027]FIG. 19 provides two perspective view examples of a multilumeninsert portion of a deep brain access device.

[0028]FIG. 20 is a perspective view example of a hub and stylets.

[0029]FIG. 21 is a perspective view example of a single peel-awaysheath.

[0030]FIG. 22 is a perspective view example of a guide bridge mountedonto a multilumen insert of a deep brain access device.

[0031]FIG. 23 is a perspective view example of an offset guide bridge.

[0032]FIG. 24 is a perspective view example of a center guide bridge.

[0033]FIGS. 25 and 26 are perspective view examples, respectively, of aremote introducer mounted onto a deep brain access device.

[0034]FIG. 27 is a perspective view alternate example of aninstrument-securing base.

[0035]FIG. 28 is a perspective view example of a ball-housing socket ona translational stage.

[0036]FIG. 29 is a perspective view example of an alternate remoteintroducer mounted to a deep brain access device.

[0037]FIG. 30 is a cross-sectional view example of an alternate deepbrain access device.

[0038]FIG. 31 is a perspective view example of a ball and inner sleevewith guide lumens.

[0039]FIG. 32 provides various perspective and cross-sectional viewexamples of a peel-away sheath with depth markers, a stylet, and a deepbrain access device receiving the sheath and stylet.

[0040]FIG. 33 provides various perspective and cross-sectional viewexamples of an alternate stabilizer.

[0041]FIG. 34 provides various perspective view examples of anotheralternate stabilizer and accompanying tool.

[0042]FIG. 35 provides various perspective and cross-sectional viewexamples of a guide alternative to the peel-away sheaths.

[0043]FIG. 36 provides a perspective and a cross-sectional view examplesof a sheath having rotatable components for allowing side access, whichis useful as an alternative to the peel-away sheath.

[0044]FIG. 37 is a cross-sectional view example of an alternative deepbrain access device, mounted to a skull, and a remote introducer mountedto the deep brain access device.

[0045]FIG. 38 is a perspective view example of an alternative deep brainaccess device providing a pivoting base, an arc-like path, and aball-and-socket movement for adjusting a trajectory of an instrumentbeing introduced into the brain.

[0046]FIG. 39 is a perspective view illustrating an alternate example ofa multilumen insert including imaging-recognizable fiducial markings.

DETAILED DESCRIPTION

[0047] The following detailed description refers to the accompanyingdrawings, which form a part of this detailed description and illustratespecific embodiments of the invention. These embodiments are describedin sufficient detail to enable those skilled in the art to practice theinvention. However, other embodiments may be used, thus structural,logical and electrical changes may be made to this description withoutdeparting from the spirit and scope of the invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,as the scope of the invention is defined only by the appended claims.

[0048] One example of trajectory guides for surgical applications isdiscussed in Truwit et al., International Patent Application No.PCT/US98/10008 (International Publication No. WO 98/51229), which isincorporated herein by reference.

[0049]FIG. 1 is a cross-sectional view illustrating an example of aflexible primary medical instrument, such as an implanted deep brainneurostimulator electrode 100. FIG. 1 also illustrates portions of asecondary medical device, such as deep brain access device 102, andportions of a patient's brain in which electrode 100 and access device102 are used. Electrode 100 includes a distal end 100A and a proximalend 100B. Proximal end 100B emerges from under a skin flap of thepatient into which it has been inserted. Access device 102 includes,among other things, a base 104 access plate or ring securedconcentrically around and/or in a burr hole 106 in the skull. Base 104provides an access opening that is approximately the same diameter as astandard burr hole. Electrode 100 extends through burr hole 106 into atarget location 108 in the brain, and is held in place by stabilizer110. Access device 102 also includes a substantially rigid cap 112 thatcovers burr hole 106, stabilizer 110, and base plate 104, and isoverlaid by a tapered low profile flexible (e.g., silicone or otherelastomer) conformal cap 114 to soften the profile of the implantedapparatuses under the patient's scalp to more closely match the skullsurface 116.

[0050] A suitable hole in conformal cap 114 and/or the overlying skinflap permits any upturned proximal portion 100B of electrode 100 to beexposed outside the skin flap, if desired. In this example, conformalcap 114 includes an engaging lip that mates with a lip of cap 112 orbase 104. This holds conformal cap 114 in place.

[0051] In one example, portions of access device 102 allow attachment byother apparatuses during targeting/alignment, positioning, and/oracutely or chronically securing the implanted instrument. Althoughdesigned for use with a trajectory alignment system, stabilizer 110 canbe used alone to stabilize catheters, needles, and drug and biologicalagent delivery instruments, as well as electrodes used for any purpose(e.g., electrical mapping, stimulation, or ablation) that have beenplaced using alternate targeting and placement methods and systems.

[0052]FIG. 2 is a perspective view of an example base 104. In thisexample, base 104 is attached to the patient's skull by any suitablefastening device, such as bone screws 200A and 200B. Alternatively, base104 is secured by threads that screw into burr hole 106. Other examplesof attachment to the skull or other portions of the patient's bodyinclude adhesive, suction and other techniques. Base 104 includes one ormore grooves 202 for receiving the proximal end 100B of electrode 100,or other flexible instrument, which is laterally bent into groove 202for conformally exiting base 104, so that proximal end 100B of electrode100 lies generally parallel to the skull surface 116. Proximal end 100Bof electrode 100 extends along skull surface 116 for a clinicallyappropriate distance. Cap 112 covers portions of burr hole 106, and theassembly of base 104 and electrode 100. In this example, base 104includes recesses 204A-B, such as for receiving respective pry lipextensions 206A-B of cap 112.

[0053]FIG. 3 is an exploded view illustrating an example of an assemblyof base 104, stabilizer 110, and cap 112. Cap 112 includes a relativelylarger top 300 and a relatively smaller, generally cylindrical base 302.Cap 112 includes male finger or female receptacle snap-fits 304 (orother attachment device(s)) that are coupled to respective mating femalereceptacle or male finger snap-fits 306 of base 104 so that, whenassembled, cap 112 is coupled to base 104, within its center opening307, and covers stabilizer 110. The cylindrical base portion 302 of cap112 includes at least one opening 308 permitting electrode 100 to exitbase 104 via groove 202.

[0054] In the example of FIG. 3, stabilizer 110 includes a disk 310coupled to a cam 312. Cam 312 rotates, with respect to disk 310, aboutan axis perpendicular to the plane of disk 310, to create andsubstantially close opening 314 in which electrode 100 is either passedfreely (when open) or clamped (when closed) Thus, cam 312 is understoodto include any form of clamping device. FIG. 3 illustrates cam 312 inits open position. Stabilizer 110 also includes snap-fits or otherfastening features for coupling it to base 104. In the example of FIG.3, stabilizer 110 can be snapped into base 104 in any rotationalorientation. That is, the user can rotate stabilizer 110 a full 360degrees to choose a specific rotational orientation with respect to base104, and then snap stabilizer 110 into base 104 at that orientation.Moreover, elongate opening 314 extends radially from the center of thedisk-like stabilizer 110 to its outer circumference. Along with the fullrotational coupling capability of stabilizer 110, this allows aninstrument, such as electrode 100, to be clamped within opening 314 inany location over the full area of opening 307 in base 104. Thisprovides additional precision in placing the electrode 100 or otherinstrument.

[0055]FIG. 4 is a perspective view illustrating a closer view ofstabilizer 110 in which cam 312 is in a closed position. FIG. 4 alsoillustrates coupling features 400A-B for coupling stabilizer 110 to base104. In this example, one or more recesses 402A-B, or other engagingfeatures, is provided. By using a tool that engages at least one ofrecesses 402A-B, stabilizer 110 can be placed into base 104 andsnap-coupled thereto. Cam 312 also includes one or more recess 404, orother engaging feature. By using a tool that engages recess 404, cam 312can be moved between open and substantially closed positions. In thisexample, cam 312 also includes a catch 406 that prevents unwantedaccidental movement of cam 312 into the open position when cam 312 isintended to be in the closed position to secure electrode 100 or othermedical instrument. In this manner, cam 312 locks into the closedposition, and is opened by pressing down on a tool engaging recess 404.This allows catch 406 to slide under disk 310.

[0056]FIG. 5 is an exploded view of an alternate embodiment in whichstabilizer 110 includes strain relief features 500A-B, either of whichmay be used to secure a small amount of slack in electrode 100 or otherinstrument. Also in this example, a plurality of grooves 202 in base104, and a corresponding plurality of grooves 308 in cap 112, allowselectrode 100 to laterally exit base 104.

[0057]FIG. 6 provides two perspective views of an example basepositioner 600 device for centering base 104 around burr hole 106 (ofknown diameter) in the skull. A distal portion 602 of positioner 600 isappropriately sized to be received into center opening 307 of base 104and further into burr hole 106. This centers base 104 concentricallyaround burr hole 106. Bone screws 200A-B are temporarily captured withinopenings in extension wings 604A-B of positioner 600, such that bonescrews 200A-B are aligned to corresponding openings in base 104. Bonescrews 200A-B are then loosely secured to the patient's skull, such thatbase 104 is properly positioned and centered around burr hole 106. Wings604A-B are scored or otherwise constructed so as to separate when bonescrews 200A-B are more securely tightened, thereby releasing bone screws200A-B so that they can fasten base 104 to the patient's skull.Positioner 600 is then removed, such as by snapping it out of base 104,leaving base 104 securely fastened in the proper position with respectto burr hole 106.

[0058]FIG. 7 is a perspective view of an example of a tool 700 forperforming procedures with respect to, among other things, base 104, cap112, and/or stabilizer 110. In this example, tool 700 includes a handle702, a first engaging arm 704, and a second engaging arm 706. The end ofarm 704 is appropriately sized to engage one of recesses 402A-B of disk310 of stabilizer 110 for placing stabilizer 110 into base 104. The endof arm 706 is appropriately sized to engage recess 404 in cam 312 formoving cam 312 between its open and closed positions. In this example,at least one of ends 704 and 706 is appropriately sized for beinginserted into one of recesses 204A-B (see FIG. 2) of base 104, and underone of corresponding extensions 206A-B for prying cap 112 away from base104.

[0059]FIG. 8 is a perspective view of an example of a different base,such as support base 800. In this example, support base 800 provides aring-like or any other (e.g., cylindrical) suitable platform 802 forsupporting other surgical equipment, such as for targeting/alignment ofthe trajectory of the instrument being introduced, and/or forintroducing the instrument after such proper alignment is obtained. Inthis example, the equipment support base 800 is separate from instrumentsecuring base 104, however, these two bases could alternatively beintegrally formed or otherwise joined. In the example of FIG. 8,however, support base 800 is secured directly to the patient's skullover and around securing base 104, using bone screws 804A-C through legsextending downward from platform 802, by using any other appropriateaffixation technique.

[0060]FIG. 9 is a perspective view of an alternate example of a base800, secured directly to the patient's skull by four bone screws 804A-Dthrough respective legs extending downward from platform 802. Thisfour-legged example advantageously allows for a smaller incision (e.g.,in the direction of the instrument exit slot of base 104) into thepatient's skull than the three-legged example of FIG. 8. Because thelegs in the example of FIG. 9 are closer together than the legs in theexample of FIG. 8, the skin does not have to be laterally spread apartas far to allow placement of the example of FIG. 9. Such a reducedlateral skin-spreading in turn reduces the required length of theincision slit.

[0061]FIG. 10 is a perspective view of an alternate example of a supportbase 800. In this example, support base 800 is secured by any suitablemeans to instrument-securing base 104, which, in turn, is secured to thepatient's skull, such as discussed above. In the example of FIG. 10,legs 1000A-D space platform 802 away from base 104. Each of legs 1000A-Dincludes one or more snap-fit features 1002 for engaging correspondingmating features on base 104. Tightening screws 1004A-B are each capturedby a respective threaded portion of platform 802, and extend downward topress against base 104 when base 104 and platform 802 are snappedtogether. By adjusting screws 1004A-B, support base 800 is backed awayfrom instrument-securing base 104 so that these two bases are moretightly coupled to each other. This provides added stability to platform802.

[0062]FIGS. 11 and 12 are perspective views of an example of atower-like instrument alignment and introduction guide assembly, alsoreferred to as a deep brain access device 1100. DBA device 1100 can alsobe regarded as including base 104, stabilizer 110, cap 112, and supportbase 800. A tower base 1102 of device 1100 snaps onto and rotates uponthe ring-like or other platform 802 of FIGS. 8-10, such as by one ormore snap-fitting side blocks 1104. Side blocks 1104 provide addedstability to prevent tower base 1102 from rocking from side-to-side onplatform ring 802. A curved saddle 1106 is coupled to and seated on acurved portion of tower base 1102, such as by at least one arcuatesliding joint, as illustrated. The curved portions of saddle 1106 andtower base 1102 can be tilted with respect to each other to alter atrajectory angle of an instrument being introduced, and can be securedto fix this aspect of the trajectory angle of the instrument.

[0063] An affixation mechanism, such as thumbscrew 1108, passes throughan opening in tower base 1102 and engages a portion of platform 802 toprevent further rotation of tower base 1102 with respect to platform 802once a desired rotational position has been obtained. In this example, acapturing device, such as L-shaped arm 1110, retains thumbscrew 1108together with tower base 1102.

[0064] Another affixation mechanism, such as thumbscrew 1112, passesthrough a slotted opening (tilt slot) in saddle 1106 and engages aportion of tower base 1102 to prevent further riding of the curvedportion of saddle 1106 along the curved portion of tower base 1102 oncea desired trajectory angle has been obtained. This example also includesattachment fasteners 1113A-B passing through corresponding slots insaddle 1106 for additionally securing saddle 1106 to tower base 1102.Attachment fasteners 1113A-B include screws passing through respectiveretainer brackets, each of which includes a curved surface conforming toa curved surface of saddle 1106.

[0065] Also in this example, an interior portion of a socket 1114 onsaddle 1106 provides a socket portion of a ball-and-socket joint. Anaffixation mechanism, such as thumbscrew 1116, passes through a threadedopening in socket 1114 to secure the position of a ball housed therein.Socket 1114 also includes fine-tuning thumbscrews 1118A-C, which passthrough threaded openings in socket 1114 for further adjusting the exactposition of a ball within socket 1114. Socket 1114 further carries amultilumen instrument guide insert assembly 1120. Multilumen insert 1120includes a tapered sleeve that is releasably coupled, by release tab1122 and associated structure(s), within a cylindrical opening throughthe spherical ball housed within socket 1114.

[0066] To release the multilumen insert 1120 from the ball, the tab 1122is pressed inward toward the sleeve. This forces or wedges a portion ofthe release tab 1122 against a top portion of the ball and aids inreleasing the multilumen insert 1120 from the ball. The top portion ofmultilumen insert 1120 provides a multilumen guide having a plurality ofopenings, such as the center opening 1124A and side openings 1124B-E;these openings are also referred to as lumens. Openings 1124B-E arespaced apart from center opening 1124A by a known predetermineddistance. Therefore, if electrode 100 is inserted through center opening1124A, and misses its target location 108 in the brain, it can beinserted into one of the side openings 1124B-E, without readjusting thetrajectory, to reach a target at a known distance away from centeropening 1124A in the plane of the multilumen insert 1120. In thisexample, multilumen insert 1120 also includes T-shaped receptacles orrecesses 1126A-D for receiving further equipment, as discussed below. Inone embodiment, multilumen insert 1120 includes one or more fiducialpoints (e.g., LEDs, reflective globes, or microcoils), such as fortrajectory alignment in a frameless surgical navigation system or in anMRI environment.

[0067]FIG. 13 is an exploded perspective view of an example of portionsof deep brain access device 1100, including instrument-securing accessbase 104, support base 800, tower base 1102, saddle 1106, socket 1114A,ball 1300, multilumen insert 1120, and other associated components. Asillustrated in FIG. 13, tower base 1102 includes a bottom or grooveportion 1302 that engages platform 802, such as using hooked side blocks1104, and allows tower base 1102 to rotate about the ring-like or otherplatform 802.

[0068]FIG. 13 also illustrates a cylindrical opening 1306 through ball1300, which is seated in socket 1114A. Multilumen insert 1120 includes atapered sleeve 1308 or barrel portion that fits snugly within opening1306. Release 1122 includes a ring portion that fits over the exteriorof sleeve 1308. To release multilumen insert 1120 from ball 1300, thetab portion of release 1122 is pressed inward toward sleeve 1308. Thisforces or wedges a portion of release 1122 against the top portion ofball 1300 and aids in releasing sleeve 1308 of multilumen insert 1120from ball 1300. The tapered barrel provided by sleeve 1308 of multilumeninsert 1120 includes, in one example, a closed end with openingscorresponding to lumens 1124A-E of multilumen insert 1120.

[0069]FIG. 14 is a perspective view illustrating an example of adjustingan instrument trajectory using portions of deep brain access device 1100with MRI, CT, PET, or another imaging modality. In FIG. 14, multilumeninsert 1120 has been removed, and an imagable reference device, such asalignment stem 1400, has been inserted into the cylindrical passagewayof ball 1300 in its place. In this example, alignment stem 1400 includesat least two fiducial points that are recognizable by the imagingmodality. The various above-described positioning mechanisms of deepbrain access device 1100 are adjusted to make the fiducial pointscollinear with the target location 108 in the brain. In one example,this may include adjusting the rotation of tower 1102 on platform 802,adjusting the tilt of saddle 1106 with respect to tower 1102, adjustingthe spherical position of ball 1300 within socket 1114, and then finetuning the exact position of ball 1300 using one or more of screws1118A-C. The imaging modality includes a computer or other processorthat provides a display indicating the relative alignment between thetrajectory of alignment stem 1400 and target location 108. This displayfurther indicates when the trajectory becomes collinear with targetlocation 108 during the positioning process. The positioning mechanismsprovide locking devices that are then locked in, and the alignment stem1400 is replaced by multilumen insert 1120 for continuing the procedureof introducing electrode 100 or other instrument along this trajectoryto target location 108 in the brain.

[0070]FIG. 15 is a perspective view illustrating an example of adjustingan instrument trajectory using portions of deep brain access device 1100in conjunction with a frameless surgical navigational system. Examplesof such systems use LEDs, light reflecting globes, or otherspatially-separated fiducial markers to establish a desired instrumenttrajectory orientation. In the frameless example of FIG. 15, multilumeninsert 1120 remains in place within the cylindrical passageway of ball1300. Adapter 1500 is inserted into center lumen 1124A of multilumeninsert 1120. In this example, adapter 1500 includes a center-bored seat1502 that snugly receives a portion of frameless navigation referencedevice instrument. The frameless navigation reference instrumentprovides spatially-separated fiducial points that are recognized by theframeless imaging modality. These fiducial points are viewed, using theappropriate imaging modality, while the various positioning mechanismsof the deep brain access device are adjusted, to orient the instrument'strajectory toward the desired target location 108 in the brain, thenlocked in. The frameless navigation instrument is then removed fromcenter-bored seat 1502 of adapter 1500. Adapter 1500 is then removedfrom center lumen 1124A of multilumen insert 1120 for continuing theprocedure of introducing electrode 100 or other instrument along thistrajectory to brain target location 108.

[0071]FIG. 16 is a perspective view illustrating an example of alignmentstem 1400 when separated from deep brain access device 1100. In thisexample, alignment stem 1400 is filled with an imagable fluid providedthrough a one-way valve 1600 at a proximal end of alignment stem 1400. Adistal end of alignment stem 1400 includes a protuberance or otherextension 1602. In this example, extension 1602 is a thin cylindricalcontainer having a distal tip 1604. Distal tip 1604 is located at thepivot point of ball 1300 when ball 1300 is seated in socket 1114 ofsaddle 1106. In this example, imagable fiducial points are provided atproximal valve 1600 and distal tip 1604. The trajectory is establishedby adjusting the various positioning mechanisms of deep brain accessdevice 1100 so that these imagable fiducial points are collinear withtarget location 108 in the brain. In one example, the exact position oftarget location 108 is obtained using real-time imaging of the brainwhile the positioning mechanisms of deep brain access device 1100 arebeing adjusted. In another example, preoperative brain images are usedto determine the position of target location 108 while adjusting thevarious positioning mechanisms of deep brain access device 1100. FIG. 16also illustrates a release mechanism 1606, which includes knob 1608 andramp 1610. By imparting a force on knob 1608 toward ball 1300, ramp 1610engages the top of ball 1300 to assist in releasing alignment stem 1400from the cylindrical passageway of ball 1300. Then, multilumen insert1120 is reinserted into the cylindrical passageway of ball 1300, forintroducing electrode 100 or other medical instrument(s) throughlumen(s) 1124 of multilumen insert 1120.

[0072]FIG. 17 is a perspective view illustrating an example of framelessadapter 1500 when separated from deep brain access device 1100. In thisexample, adapter 1500 includes stainless steel pin, having a distal tip1700, that is appropriately sized for being inserted into center lumen1124A of multilumen insert 1120. When fully inserted, distal tip 1700 islocated the pivot point of ball 1300 when ball 1300 is seated in socket1114 of saddle 1106. In this example, a frameless navigation instrumentwith frameless imagable fiducial points is inserted into center-boredseat 1502 at the proximal end of adapter 1500, or onto the outer portionof adapter 1500, or otherwise coupled to adapter 1500 by any otherappropriate coupling technique.

[0073]FIG. 18 is a perspective view illustrating an example of atechnique for introducing an instrument along the previously establishedtrajectory to target location 108 in the brain. In FIG. 18, multilumeninsert 1120 is used to guide a distal end of a secondary medicalinstrument, such as an elongate lumenal catheter or peel-away sheath,for example, one of sheaths 1800A-C, toward target location 108. Beforesheath 1800 is inserted into one of lumens 1124A-E of multilumen insert1120, however, a stylet is inserted through a hollow center bore orlumen of sheath 1800. This prevents coring of brain tissue by the hollowcenter bore of sheath 1800 and, in one embodiment, provides additionalrigidity for performing the insertion and obtaining an accurate pathalong the established trajectory toward target location 108.

[0074] The example of FIG. 18 illustrates a triple sheath assembly 1802,with linearly-arranged sheaths 1800A-C, appropriately spaced apart forbeing inserted into three linearly-arranged lumens 1124 of multilumeninsert 1120. This example similarly illustrates a triple stylet assembly1804 in which three linearly-arranged stylets are spaced apart forinsertion in the linearly-arranged sheaths 1800A-C. This triplesheath/stylet illustration is merely an example. The exact number ofsheaths 1800 and corresponding stylets being introduced ranges from asingle sheath/stylet to the number of available lumens 1124 inmultilumen insert 1120. After sheath assembly 1802 and stylet assembly1804 has been guided approximately to target location 108, styletassembly 1804 is removed and a guide bridge is secured to multilumeninsert 1120 for guiding electrode 100 into the center bore of one ofsheaths 1800A-C for positioning electrode 100 at target location 108.The sheaths 1800A-C are then removed by pulling apart handles 1806A-B.In the illustrated example, each sheath 1800 breaks into two pieces asit is being extracted.

[0075]FIG. 19 provides two perspective views of an example of multilumeninsert 1120, which includes the tapered barrel-like sleeve 1308 that isinserted into center hole 1306 of ball 1300. Lumens 1124A-E extend fromthe top of multilumen insert 1120 through the barrel sleeve 1308. Asdiscussed above, side lumens 1124B-E are appropriately radially-spaced(e.g., 3 millimeters, center-to-center) from center lumen 1124A toprovide capability for repositioning of electrode 100 by a known amountby simply removing electrode 100 from center lumen 1124A and reinsertingit into a desired one of side lumens 1124B-E. FIG. 19 also illustratesreceptacles 1126A-D, opposing pairs of which are used for receiving aguide bridge or other equipment desired to be mounted to the top ofmultilumen insert 1120.

[0076]FIG. 20 is a perspective view illustrating an alternate example ofa stylet assembly 2000, including a hub 2002 for uniting 1-5 stylets2004A-C for insertion into corresponding peel-away or other sheathsinserted through corresponding lumens 1124 of multilumen insert 1120. Inone embodiment, hub 2002 includes a Touhy-Borst adapter, or othersuitable adapter for gripping stylets 2004A-C.

[0077]FIG. 21 is a perspective view illustrating an example of a singlepeel-away sheath 2100 including a distal tip 2102, a proximal end 2104,and a center bore or lumen extending therebetween. Handles 2106A-B areincluded at proximal end 2104. Sheath 2100 is peeled away and extractedby pulling apart handles 2106A-B.

[0078]FIG. 22 is a perspective view illustrating an example of a guidelumen selector, such as guide bridge 2200 having tabs or legs that aresnap-mounted onto an opposing pair of receptacles 1126A-D of multilumeninsert 1120. In this example, guide bridge 2200 includes a cylindricalguide tube 2202 extending upward from a base portion of guide bridge2200. Guide tube 2202 includes a center bore hole 2204 for passingelectrode 100 or other instrument therethrough. A proximal portion ofguide tube 2202 includes a lip 2206 extending outward circumferentiallyaround the perimeter of guide tube 2202. In one example, the center borehole 2204 is tapered inward in a direction away from lip 2206. That is,an inner diameter of bore hole 2204 necks down so the instrument passedtherethrough is automatically centered as it approaches the base portionof guide bridge 2200. In this example, guide bridge 2200 also assists inholding the sheath(s) in place as the electrode is being passed througha sheath to target location 108. The handle portions of the sheath donot pass through guide tube 2202, but instead, exit under the sides ofguide bridge 2200. In one example, guide bridge 2200 includes awedge-like ridge on its underside to assist in splitting the peel-awaysheath.

[0079]FIGS. 23 and 24 are perspective views illustrating an offset guidebridge 2300 and a center guide bridge 2400, respectively. Lumens 1124A-Eprovide a primary guide device for electrode 100 or other instrument,and the selected one of offset guide bridge 2300 and center guide bridge2400 provides a secondary guide device for electrode 100 or otherinstrument. Offset guide bridge 2300 is selected when the instrumentbeing introduced is intended to pass through one of side lumens 1124B-Ein multilumen insert 1120. In this example, guide tube 2202 is offsetfrom the center of the base of offset guide bridge 2300, such that itscenter bore 2204 is aligned with one of side lumens 1124B-E ofmultilumen insert 1120. Alignment with the particular desired side lumenis obtained by appropriately rotating the orientation of offset guidebridge 2300 and snapping tabs 2302A-B into corresponding opposing pairsof receptacles 1126. By contrast, in center guide bridge 2400, guidetube 2202 is centered on the base portion of center guide bridge 2400,such that its center bore 2204 aligns with center lumen 1124A ofmultilumen insert 1120 when center guide bridge 2400 is snapped intoopposing pairs of receptacles 1126 of multilumen insert 1120. In each ofthe examples of FIGS. 23 and 24, an outside portion of lip 2206 isthreaded for engaging other equipment. Alternatively, other equipmentmay be mounted onto guide tube 2202 by using a compression fit to athreaded or unthreaded lip 2206.

[0080]FIGS. 25 and 26 are perspective views of deep brain access device1100, on which a center guide bridge 2400 is mounted to multilumeninsert 1120. In these examples, an introducer 2500 mechanism is mountedonto guide tube 2202 using a compression fitting to lip 2206. Introducer2500 includes a slide 2502 mechanism on which a sliding clamp 2504 ridestoward and away from deep brain access device 1100 and, therefore,toward and away from burr hole 106 in the skull or other entry portal.Clamp 2504 holds the electrode 100 or other instrument being introduced.In one example, introducer 2500 is operated remotely by controls 2506A-Bto slide clamp 2504 along slide 2502, and therefore, to introduce theinstrument being held by clamp 2504 into and/or out of the brain alongthe predetermined trajectory in a controlled manner. One example of anappropriate remote introducer 2500 is the Fathom® Remote Introduceravailable from Image-Guided Neurologics, Inc. of Melbourne, Fla. U.S.A.Another example of an appropriate remote introducer 2500 is described inSkakoon et al. U.S. patent application Ser. No. ______, entitled“Medical Device Introducer,” filed on Apr. 5, 2001 and assigned to theassignee of the present patent application, the disclosure of which isincorporated herein by reference in its entirety.

[0081]FIG. 27 is a perspective view of an alternate example of aninstrument-securing base 2700. In this example, base 2700 is centeredaround burr hole 106 and secured to the skull using bone screws 2702A-Dextending through openings in leg portions. Base 2700 includes twoopposing mating slides 2704A-B that move toward and away from eachother, and that mate and engage each other to clamp electrode 100 orother instrument therebetween. One or more slots 202 are provided forproviding a lateral exit for electrode 100, as discussed above. Otherequipment is either attached directly to the skull around base 2700, orattached indirectly to the skull, though base 2700, such as by snappingor clamping such equipment to receiving sides 2706A-B.

[0082]FIG. 28 is a perspective view of a ball-housing socket 2800, usedas an alternative to socket 1114. In this example, socket 2800 rides ona sliding translational stage 2802 on a mount 2804 coupled to saddle1106 or other portion of deep brain access device 1100. This exampleincludes a squeeze release 2806 for disengaging mount 2804 from saddle1106 or other affixation point of deep brain access device 1100.Alternatively, mount 2804 is affixed to securing base 2700 by a hookedengagement mechanism 2808 that engages an underside of securing base2700, or by using any other appropriate coupling technique. Thumbscrew2810 engages a threaded opening in mount 2804 and also engages andcontrols translational movement of sliding stage 2802. Thumbscrew 2812engages a threaded opening in mount 2804 and secures the position ofstage 2802 to prevent unwanted translational movement after its desiredposition is obtained. Either thumbscrew may be captured to preventaccidental separation from mount 2804.

[0083]FIG. 29 is a perspective view illustrating a remote introducer2900, provided as an alternative to introducer 2500. In this example,introducer 2900 is coupled to a portion of deep brain access device2901, such as by using a Touhy-Borst adapter 2902 threaded onto a lip ofa guide tube, similar to lip 2206 of guide tube 2202. In this example,electrode 100 is inserted through a peel-away sheath 2100 (afterremoving a stylet). Sheath 2100 is secured to a squeeze-release clamp2904 that slides toward and away from the skull along slide 2906. Inthis example, advancement and retraction of clamp 2904 is remotelycontrolled using controls 2506A-B.

[0084]FIG. 30 is a cross-sectional view illustrating a deep brain accessdevice 3000, provided as an alternative to deep brain access device1100. In this example, base 104 is secured to the skull using bonescrews. A pedestal or tower 3002 is secured to base 104 as illustratedor, alternatively, is secured directly to the skull. Tower 3002 includesa socket 3004 housing a ball 3006. Ball 3006 includes a center openingthat receives a rotating inner barrel sleeve 3008. In this example,sleeve 3008 includes one or more lumens 3010A-C extending therethroughfor passing and guiding instruments, sheaths, stylets, etc. Anaffixation device, such as thumbscrew 3012, fixes the position of ball3006 when the desired trajectory alignment has been obtained, such as byusing the MRI, CT, PET, or frameless navigational guidance techniquesdiscussed above. Proximal portions of lumens 3010A-C include recessesfor snapping into place lips on devices inserted therein, such asalignment stem (or frameless adapter) 3014 and/or Luer stem 3016. Aremote introducer may be attached to Luer stem 3016, as discussed above.Luer stem 3016 may include a wedge 3018, for assisting in splitting apeel-away sheath inserted through corresponding lumen 3010 before Luerstem 3016 is inserted therein. Luer stem 3016 may also includeorientation tabs 3020 to appropriately align the wedge to provide thedesired assistance in splitting the peel-away sheath.

[0085]FIG. 31 is a perspective view illustrating an example of ball 3006and sleeve 3008, including an illustration of the ball-and-socketmovement of ball 3006 and rotational movement of sleeve 3008 within ball3006. In this example, lumens 3010 include associated transverse grooves3100 extending laterally in opposite directions from the lumens 3010 toopposing edges of sleeve 3008. Grooves 3100 receive and/or holdpeel-away portions of one or more peel-away sheaths inserted intorespective lumens 3010.

[0086]FIG. 32 provides various perspective and side views of portions ofdeep brain access device 3000 and associated components. In thisexample, a three prong titanium stylet 3200 assembly is inserted intocorresponding lumens of a triple peel-away plastic sheath 3202 assembly.One or more prongs of sheath 3202 includes depth markers 3204. Thecombined sheath 3202 and stylet 3200 is inserted into correspondinglumens 3010 of guide sleeve 3008 to the desired depth, as indicated bydepth markers 3204 on sheath 3202. The proximal portion of sheath 3202is then separated as illustrated in FIG. 32 and flattened out laterally.Wedge 3206 on a proximal handle portion of stylet 3200 may assist insplitting sheath 3202. This establishes the prongs of sheath 3202 at thedesired depth. Stylet 3200 is then removed, and electrode 100 or anotherinstrument is introduced into position through the sheath 3202.

[0087]FIG. 33 provides exploded perspective and cross-sectional views ofa stabilizer 3300, which can serve as an alterative to stabilizer 110.In this example, stabilizer 3300 includes a substantially rigidring-like base 3302, a substantially rigid upper plate, 3304, and a softmiddle plate 3306 interposed between upper plate 3304 and lower ring3302. Upper plate 3304 and middle plate 3306 include correspondingopenings 3308. A neurostimulating electrode 100 or other instrument ispassed through one of these openings 3308. A soft male protuberancearound the opening in middle plate 3306 is received within a femalereceptacle around the opening in upper plate 3304. When upper plate 3304is clamped down against base 3302, the soft protuberance is squeezedagainst the electrode 100, holding it securely in place.

[0088]FIG. 34 is a perspective view of an stabilizer 3400, whichprovides an alternative to stabilizer 110. In this example, stabilizer3400 is rubber or any other flexible material that tends to return toits original shape. A spreader 3402 is used to open a slot 3406 instabilizer 3400, which is then inserted into an instrument-securingbase-plate fastened to the skull. When electrode 100 or other instrumentis properly positioned, the spreader is removed, allowing stabilizer3400 to return to its original shape with the slot 3406 closed aroundthe electrode 100 to hold it securely in place.

[0089]FIG. 35 provides a perspective view and several cross-sectionalviews illustrating a sheath-substitute guide 3500, which provides analternative to the peel-away sheaths discussed above. In this example,guide 3500 includes one or more elongate guides 3500A-C that do not havea central bore lumen for guiding an instrument through. Instead, eachguide 3500A-C includes a cross-section that is formed for guiding aninstrument along its side. In this example, the cross-section iscrescent-shaped so as to provide a degree of mating to the outerdiameter of electrode 100, stylet 3502, or other instrument that isintroduced into the patient along the side of the guide 3500. In oneexample, guide 3500 is introduced in tandem with removable stylet 3502,which provides additional rigidity to the introduction process. Inanother example, guide 3500 is introduced without removable stylet 3502.Because guide 3500 does not use a central bore lumen, coring of braintissue during its introduction may be of less concern. Guide 3500 allowsaccess to the adjacent electrode 100 along its entire length, allowingelectrode 100 to be gripped and/or secured very close to the skull (suchas using instrument-securing base 104) before guide 3500 is removed.This prevents excessive movement of electrode 100 during extraction ofguide 3500, which provides more accurate placement of electrode 100 orother instrument.

[0090]FIG. 36 provides a perspective view and a cross-sectional viewillustrating a sheath 3600 assembly, which provides another alternativeto the peel-away sheaths discussed above. In this example, sheath 3600assembly includes one or more elongate sheaths 3600A-C. Each elongatesheath 3600 includes an open slot along its length, or a portionthereof. In the illustrated example, each elongate sheath 3600 includestwo C-shaped portions 3602A-B that rotate with respect to each other bymanipulating a handle portion of the sheath 3600. When the C-shapedportions 3602A-B are rotated into a closed position, they togethereffectively provide a central lumen 3604 through which electrode 100 orother instrument may be passed. When the C-shaped portions 3602A-B arerotated into an open position, they together effectively provide an openslot along their length, allowing access to electrode 100 or otherinstrument that has been inserted therethrough. This allows electrode100 to be gripped and/or secured very close to the skull (such as usinginstrument-securing base 104) before sheath 3600 is removed. Thisprevents excessive movement of electrode 100 during extraction of sheath3600, which provides more accurate placement of electrode 100 or otherinstrument. In this example, stylet(s) may be inserted into the lumen3604 before sheath 1600 is introduced, to avoid coring of brain tissue.

[0091]FIG. 37 is a cross-sectional view illustrating an example of deepbrain access device 3000 mounted onto the patient's skull with remoteintroducer 2500 mounted onto Luer stem 3016, which is snapped intocentral lumen 3010B. Neurostimulating electrode 100 is held byintroducer 2500, and passed through central lumen 3010B to targetlocation 108 of the brain.

[0092]FIG. 38 is a cross-sectional view illustrating an alternateexample of a deep brain access device 3800. This example illustrates abase 3802, which is centered around burr hole 106 and secured to theskull. A tower 3804 is secured to base 3802 or, alternatively, directlyto the skull. Tower 3804 includes mounting legs 3806 and 3808, which areaffixed to base 3802 or to the skull. The mounting legs 3806 and 3808are coupled to a pedestal 3810 by pivot pins 3812 and 3814. Pins 3812and 3814 are aligned to provide a longitudinal axis about which pedestal3810 pivots until locked in place by thumbscrew 3816, which engages oneof the pins 3812 and 3814. Thus, pedestal 3810 would be capable ofpivoting into and out of the drawing of FIG. 38.

[0093] In the example of FIG. 38, pedestal 3810 includes an arc 3818extending between leg extensions 3820A-B that are coupled to pivot pins3812 and 3814. Arc 3818 is curved, so that a center portion 3822, awayfrom leg extensions 3820A-B, would be more distant from the viewer ofFIG. 38 than the portions of arc 3818 that are closer to leg extensions3820A-B. Arc 3818 includes a slot 3824 extending substantially along itslength between leg extensions 3820A-B. A socket 3826 engages and ridesalong slot 3824, until locked into position by securing thumbscrew 3828against arc 3818. Socket 3826 houses a ball 3006 that can be adjustedspherically until locked into place by one or more thumbscrews. Ball3006 includes a center sleeve 3008 having one or more lumens, asdiscussed above with respect to FIG. 30. In the example of FIG. 38, aLuer stem 3016 is snapped into a center lumen of sleeve 3008, and aremote introducer 2500 is mounted onto the Luer stem for guidingelectrode 100 to target location 108.

[0094]FIG. 39 is a perspective view illustrating an alternate example ofa multilumen insert 1120. In this example, multilumen insert 1120includes one or more fiducial markers 3900A-C (e.g., LEDs, reflectiveglobes, or MRI-imagable microcoils), such as for trajectory alignment ina frameless surgical navigation system or in an MRI environment. Thisillustration shows three such imagable fiducial markers 3900A-C defininga plane. Fiducials 3900A-C are supported on respective arms extendingfrom an attachment extension 3902, which is coupled by an fastener, suchas screw 3904, to an aim 3906 that extends upward and outward from theplanar face plate 3908 of multilumen insert 1120. This coupling isperformed (e.g., using integral alignment guides or, alternatively,performing a calibration adjustment) so that a predetermined knownspatial relationship exists between the plane formed by imagablefiducials 3900A-C and the plane of face plate 3908, which is orthogonalto the instrument trajectory axis through each of lumens 1124A-E.Consequently, imaging fiducials 3900A-C are viewed in conjunction withadjusting the various positioning mechanisms of the deep brain accessdevice to obtain and fix the desired instrument trajectory with respectto the entry portal. Although, in this example, imaging fiducials3900A-C are illustrated as being attached and in a known spatialrelationship to plate 3908, imaging fiducials 3900A-C may alternativelybe attached to any other component of the deep brain access device so asto establish a known spatial relationship between the fiducials 3900A-Cand an axial trajectory provided by one or more of lumens 1124A-E. Asanother alternative, any component of the deep brain access deviceincludes an adapter for receiving one of several commercially availablesurgical navigation instruments. Such surgical navigation instrumentssimilarly provide imaging-recognizable fiducials. Such an adapter shouldbe oriented such that the spatial relationship between the surgicalnavigation instrument and the instrument trajectory is known, therebyallowing imaging of the fiducials to assist in adjusting the trajectoryto target location 108.

[0095] The discussed devices and methods may be used in with framelesssurgical navigation or with MRI or other imaging. Such techniques permitreal-time determination and confirmation of anatomical placement of theinstrument for improving targeting and placement accuracy. Otheradvantages include, among other things, an alignment apparatus that usesa localized coordinate system in which positioning and aligning is basedon a coordinate system relative to the patient's skull and the skullentry point rather than a stereotactic frame; real-time imaging thateliminates the need for retrospective imaging and also allows directconfirmation of the anatomical placement; an anatomically determinedinitial targeting angle (the angle between the body or skull surface andthe theoretical target) that is selected based on the patient's actualanatomy; a unique center-of-arc principle using rotation about thenominal trajectory axis, thus simplifying optimization of the firstangular adjustment; a locking ball-and-socket arrangement for easy andaccurate direct targeting under real-time imaging or frameless surgicalnavigation; peel-away or alternative sheaths that allow the device to beeasily secured into position; access to the base plate assembly so thatthe electrode can be captured at the surface of the skull immediatelyafter successful placement and before disassembly of the targetingapparatus; and visible (under the imaging method chosen, e.g., under CTor MRI) alignment stems.

[0096] Similarly, the stabilization system provides for in situstabilization immediately upon proper placement, through use of a diskand cam arrangement, thus eliminating inadvertent movement duringdisassembly of the alignment apparatus, and reducing the likelihood ofthe electrode moving after implantation; the snap-fit solid cap protectsthe electrode and its capture mechanism from damage; the stabilizationsystem is substantially scaled to minimize ingress and egress; the baseplate is securely attached to the body; a special tool facilitatesplacement of the base plate correctly into the burr hole, thus assuringadequate clearance for proper assembly of all parts, as well aspre-positioning apparatus for easy attachment; and the electrode iscaptured by clamping it in a gap between two parts, therefore electrodedamage cannot occur because the gap size is limited by a physical stop.

[0097] Although the examples primarily discuss targeting, placement, andstabilization of a deep brain electrode, this is just an example of oneof the possible procedures that can be done using the body portal typetrajectory guide. Numerous other procedures will be accomplished usingthis device. In addition, the device will give rise to other futuresurgical procedures.

[0098] It is to be understood that the above description is intended tobe illustrative, and not restrictive. For example, the above-describedembodiments may be used in combination with each other. Many otherembodiments will be apparent to those of skill in the art upon reviewingthe above description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. In the appendedclaims, the terms “including” and “in which” are used as theplain-English equivalents of the respective terms “comprising” and“wherein.

What is claimed is:
 1. A method including: securing a base portion of aguide lumen carrying assembly around an entry portal in a surface;rotating at least a portion of the guide lumen carrying assembly about afirst axis that is substantially concentric to the entry portal andsubstantially orthogonal to the surface; and tilting at least a portionof the assembly so that a second axis, extending concentrically throughthe guide lumen, is at a desired angle with the first axis.
 2. Themethod of claim 1, further including spherically adjusting a portion ofthe guide-lumen carrying assembly to orient a trajectory provided by thesecond axis in a desired direction with respect to the entry portal. 3.The method of claim 2, further including fixing a position of the guidelumen.
 4. The method of claim 3 in which fixing the position of theguide lumen includes at least one of: securing the rotating portion ofthe guide-lumen assembly; securing the tilting portion of theguide-lumen carrying assembly; and securing the spherically adjustableportion of the guide lumen carrying assembly.
 5. The method of claim 2,in which spherically adjusting includes adjusting an orientation of aball housed in a socket.
 6. The method of claim 5, in which sphericallyadjusting includes moving a position of the ball within the socket usingat least one threaded member engaging the ball.
 7. The method of claim1, further including fixing a position of the guide lumen.
 8. The methodof claim 1, further including introducing an instrument through theguide lumen and the portal substantially along a trajectory provided bythe second axis.
 9. The method of claim 8, in which introducing theinstrument includes introducing at least one instrument selected fromthe group consisting essentially of a sheath, a stylet, a guide, aprimary medical instrument, and an electrode.
 10. The method of claim 8,in which introducing the instrument includes: coupling a sliding clampto a portion of the guide-lumen carrying assembly; clamping a portion ofthe instrument to the clamp; and advancing the sliding clamp toward theentry portal.
 11. The method of claim 8, in which introducing theinstrument includes: inserting a stylet into a lumen of a sheath; andadvancing the stylet and sheath through the guide lumen and the entryportal.
 12. The method of claim 11, further including removing thestylet from the lumen of the sheath.
 13. The method of claim 12, furtherincluding inserting an electrode into the lumen of the sheath andthrough the guide-lumen and through the entry portal.
 14. The method ofclaim 13, further including retracting the sheath from the entry portalby peeling the sheath into more than one piece.
 15. The method of claim13, further including adjusting a distance by which the sheath extendsinto the entry portal by viewing an indicator on the sheath.
 16. Themethod of claim 1, further including receiving, into the guide-lumen, aportion of an imagable device.
 17. The method of claim 16, in whichreceiving the portion of the imagable device includes receiving animagable device selected from the group consisting essentially of anMRI-imagable alignment stem, a CT-imagable alignment stem, and aframeless surgical navigation instrument.
 18. The method of claim 16, inwhich the rotating and tilting are performed in conjunction withreal-time viewing of the imagable device, using a corresponding imagingmodality, to align a trajectory of the second axis with a targetlocation located through the entry portal beyond the surface.
 19. Themethod of claim 1, further including: securing a base access plate tothe surface around the entry portal; introducing an instrument throughthe entry portal to a target location beyond the surface; and securingthe introduced instrument to the base access plate.
 20. The method ofclaim 19, further including concentrically aligning the base accessplate to the entry portal.
 21. The method of claim 20, in which thealigning includes: inserting a screw-carrying positioner through anopening in the base access plate and into the entry portal to positionthe base access plate concentrically around the entry portal; screwingthe base access plate to the surface, thereby releasing the screws fromthe screw-carrying positioner; and removing the positioner.
 22. Themethod of claim 19, in which securing the introduced instrument includesclamping the introduced instrument.
 23. The method of claim 19, furtherincluding laterally exiting the instrument from the base plate.
 24. Themethod of claim 1, further including capping the entry portal.
 25. Themethod of claim 1, further including introducing an instrument throughthe guide lumen and the entry portal toward a target location beyond thesurface of the entry portal.
 26. The method of claim 25, in which theguide lumen is a first guide lumen, and further including reintroducingthe instrument through a second guide lumen offset from the first guidelumen by a predetermined distance.
 27. The method of claim 1, in whichthe guide lumen carrying assembly provides a plurality of guide lumens,and further including selecting a particular one of the guide lumens forintroducing an instrument by at least one of orienting and coupling aguide lumen selector to the guide lumen carrying assembly.
 28. A methodincluding: securing a base access plate to a surface around an entryportal; introducing an instrument through the entry portal to a targetlocation beyond the surface; and securing the introduced instrument tothe base access plate.
 29. The method of claim 28, further includingconcentrically aligning the base access plate to the entry portal. 30.The method of claim 28, in which the aligning includes: inserting ascrew-carrying positioner through an opening in the base access plateand into the entry portal to position the base access plateconcentrically around the entry portal; screwing the base access plateto the surface, thereby releasing the screws from the screw-carryingpositioner; and removing the positioner.
 31. The method of claim 28, inwhich securing the introduced instrument includes clamping theintroduced instrument.
 32. The method of claim 28, in which securing theintroduced instrument includes: selecting an orientation of astabilizing clamp from a full 360 degree range of available orientationswith respect to the base access plate; and coupling the stabilizingclamp to the base access plate in the selected orientation.
 33. Themethod of claim 32, further including: selecting a radial position ofthe introduced instrument in an elongate opening extending from a centerregion of the stabilizing clamp; and clamping the introduced instrumentat the selected radial position.
 34. The method of claim 28, furtherincluding laterally exiting the instrument from the base plate.
 35. Themethod of claim 28, further including capping the entry portal.
 36. Themethod of claim 28, further including: securing a base portion of aguide lumen carrying assembly around an entry portal in a surface;rotating at least a portion of the guide lumen carrying assembly about afirst axis that is substantially concentric to the entry portal andsubstantially orthogonal to the surface; and slidably tilting at least aportion of the assembly so that a second axis, extending concentricallythrough the guide lumen, is at a desired angle with the first axis. 37.A method including: securing a base portion of a multiple primary guidelumen carrying assembly around an entry portal in a surface; orienting asecondary guide lumen, with respect to a plurality of coupling locationsof the primary guide lumen carrying assembly, such that the secondaryguide lumen aligns with a desired one of the multiple primary guidelumens; and coupling the secondary guide lumen to the primary guidelumen carrying assembly in the selected orientation.
 38. The method ofclaim 37, further including introducing an instrument through thesecondary guide lumen and the aligned one of the primary guide lumens.39. The method of claim 38, further including: introducing a sheath intothe aligned one of the primary guide lumens; and holding the sheath atthe secondary guide lumen as the instrument is inserted through thesecondary guide lumen and the aligned one of the primary guide lumensthrough the sheath.
 40. The method of claim 39, further includingsecuring the instrument near the secondary guide lumen before removingthe sheath.
 41. The method of claim 40, in which removing the sheathincludes pulling the sheath out in a plurality of pieces.
 42. A methodincluding: introducing a sheath through a portal in a surface to atarget location; introducing an instrument through the sheath to thetarget location; rotating first and second portions of the sheath withrespect to each other to create an access opening in the sheath abovethe surface of the portal, thereby exposing a portion of the instrument;securing an exposed portion of the instrument; and removing the sheath.43. A method including: securing a base portion of a guide lumencarrying assembly around an entry portal in a surface, the guide lumenproviding a trajectory axis, and the body portal providing a portalnormal axis that is orthogonal to the surface of the body portal;adjusting an angle between the trajectory axis and the portal normalaxis by pivoting an arcuate portion of the guide lumen carrying assemblywith respect to the base; and adjusting the angle between the trajectoryaxis and the portal normal axis by sliding a portion of the guide lumencarrying assembly along the arcuate portion of the guide lumen carryingassembly.
 44. The method of claim 43, further including sphericallyadjusting the guide lumen with respect to the arcuate portion of theguide lumen carrying assembly.
 45. The method of claim 43, furtherincluding introducing a primary medical device along the trajectoryaxis.
 46. An access device including: a mounting unit having a mountingplane; and a primary guide assembly that defines at least one insertionaxis, the guide assembly being attached to the support structure by atleast one joint.
 47. The access device of claim 46, in which the atleast one joint includes a rotating joint allowing rotation of theprimary guide structure about a rotation axis normal to the mountingplane.
 48. The access device of claim 47, further including a firstlocking device that fixes an orientation of the rotating joint.
 49. Theaccess device of claim 47, in which the at least one joint includes anarcuate sliding joint capable of adjusting an insertion angle of atleast one insertion axis with respect to the mounting plane.
 50. Theaccess device of claim 49, in which the at least one joint includes aball and socket joint, coupled to the arcuate sliding joint, allowingfurther adjustment of the insertion angle.
 51. The access device ofclaim 50, further including a third locking device that fixes the balland socket joint within a range of motion.
 52. The access device ofclaim 50, in which the primary guide assembly is detachable from theball-and-socket joint, a portion of the primary guide assembly fittingwithin a ball of the ball-and-socket joint using a tapered outsidesurface so that the primary guide assembly is held in the ball by awedge formed by the tapered outside surface.
 53. The access device ofclaim 50, in which the ball-and-socket joint further includes aplurality of ball adjustment contacts, each ball adjustment contactbeing adjustable with respect to a socket of the ball-and-socket joint,and each ball adjustment contact being in communication with the ball.54. The access device of claim 53, in which the plurality of balladjustment contacts include threaded members that are threaded throughthe socket, and contact the ball.
 55. The access device of claim 49,further including a second locking device that fixes the insertion anglewithin a range of motion.
 56. The access device of claim 46, furtherincluding a reference device coupled to the primary guide assemblywherein the reference device locates at least one of the insertion axes.57. The access device of claim 56, in which the reference deviceincludes a number of light emitting diodes.
 58. The access device ofclaim 56, in which the reference device includes a number of lightreflectors.
 59. The access device of claim 56, in which the referencedevice includes one or more electrical coils.
 60. The access device ofclaim 46, in which at least one insertion axis includes a centralinsertion axis and a peripheral insertion axis.
 61. The access device ofclaim 46, in which at least one insertion axis includes a centralinsertion axis and four peripheral insertion axes.
 62. The access deviceof claim 46, further including a secondary guide device, having asecondary insertion axis, the secondary guide device being coupled tothe primary guide assembly.
 63. The access device of claim 62, in whichthe secondary insertion axis is collinear with the central insertionaxis.
 64. The access device of claim 62, in which the secondaryinsertion axis is collinear with one of the peripheral insertion axes.65. An access system including: an access device including: a mountingunit having a mounting plane; a primary guide assembly that defines atleast one insertion axis, the guide assembly being attached to themounting unit by at least one joint; and an alignment device coupled tothe primary guide assembly, a portion of the alignment device beingvisible using an imaging device.
 66. The access system of claim 65, inwhich the alignment device includes a fluid filled stem that is visibleusing magnetic resonance imaging (MRI).
 67. The access system of claim65, further including a processor that indicates when the insertion axisis aligned with a target within a patient.
 68. An access systemincluding: an access device including: a mounting unit having a mountingplane; a primary guide assembly that defines at least one insertionaxis, the guide assembly being attached to the mounting unit by at leastone joint; and at least one sheath adapted for insertion through theprimary guide assembly.
 69. The access system of claim 68, furtherincluding at least one stylet adapted for insertion through the at leastone sheath.
 70. The access system of claim 69, in which the sheathcovers a first longitudinal portion of the stylet, leaving a secondlongitudinal portion of the stylet exposed.
 71. The access system ofclaim 68, in which the sheath includes a peel-away portion.
 72. Theaccess system of claim 68, in which the sheath includes: a first sheathportion; and a second sheath portion capable of rotating with respect tothe first sheath portion such that when rotated from a first position toa second position a longitudinal sheath opening is exposed.
 73. Anaccess system including: an access device including: a mounting unithaving a mounting plane; a primary guide assembly that defines at leastone insertion axis, the guide assembly being attached to the mountingunit by at least one joint; and a device introducer that controllablymoves a primary device along the insertion axis.
 74. The access systemof claim 73, in which the device introducer includes a locally mountedindicator device that is capable of locating a position of a primarymedical device along the insertion axis.
 75. The access system of claim74, in which the locally mounted indicator device includes at least oneof a linear encoder and a potentiometer.
 76. An access system including:an access device including: a mounting unit having a mounting plane; aprimary guide assembly that defines at least one insertion axis, theguide assembly being attached to the mounting unit by at least onejoint; and a fixing device coupled to the mounting unit, the fixingdevice being capable of fixing the location of a primary device alongthe insertion axis.
 77. The access system of claim 76, wherein thefixing device includes: a body, the body having an opening with a firstsurface; a fixing unit, the fixing unit having a second surface that isadjustable with respect to the first surface; and a locking devicecapable of holding the fixing unit in a position with respect to thebody such that the first and second surfaces engage the primary medicaldevice, fixing it in a location along the insertion axis.
 78. The accesssystem of claim 77, further including a cap that is capable ofsubstantially covering an insertion opening in the mounting unit. 79.The access system of claim 78, further including a groove that allows aprimary device to remain fixed in a location along the insertion axis,while the insertion opening is covered with the cap.
 80. The accesssystem of claim 76, further including a removable centering device, theremovable centering device including: a centering body; a number ofinsertion opening contacts coupled to the centering body; and anattachment device that is removably coupled to the mounting unit duringa mounting procedure.
 81. An access device including: a mounting unithaving a mounting plane; a primary guide assembly that defines at leastone insertion axis, the guide assembly being attached to the supportstructure by a number of joints including: a pivot joint capable ofadjusting a first insertion angle of at least one insertion axis withrespect to a first direction in the mounting plane; and an arcuatesliding joint capable of adjusting a second insertion angle of at leastone insertion axis with respect to a second direction in the mountingplane.
 82. The access device of claim 81, further including aball-and-socket joint, coupled to the arcuate sliding joint, allowingfurther adjustment of the orientation of the primary guide assembly. 83.The access device of claim 82, further including a device introducercoupled to the primary guide assembly that controllably moves a primarydevice along the insertion axis.
 84. A primary device retention systemincluding: a base having a mounting plane and an insertion opening, thebase being capable of being attached to a body; and a fixing devicecoupled to the base, the fixing device being capable of fixing thelocation of a primary device within the body.
 85. The system of claim84, wherein the fixing device includes: a first portion, the firstportion having an opening that includes a first surface; a secondportion, the second portion having a second surface that is adjustablewith respect to the first surface; and a locking device capable ofholding the second portion in a position with respect to the firstportion such that the first and second surfaces engage the primarydevice, fixing it in a location within the body.
 86. The system of claim85, in which the fixing device is coupled to the base such that thefixing device is capable of rotating about an axis normal to themounting plane.
 87. The system of claim 86, in which the first surfaceincludes a radially oriented planar surface.
 88. The system of claim 87,in which the base includes: at least one opening to accommodate aproximal portion of the primary device; the fixing device being capableof rotating the radially oriented planar surface into alignment with theat least one opening and fixing the location of the primary devicewithin the body while the proximal portion of the primary device isrouted in the at least one opening.
 89. The system of claim 84, furtherincluding a cap that is capable of covering the insertion opening in thebase.
 90. A device for immobilizing a primary instrument, including:abase; and attached to the base, a stabilizer to engage the instrument,the stabilizer including a movable cam to define an opening sized andshaped to immobilize the instrument.
 91. A device for immobilizing aprimary instrument, including: a base; a resilient lower platestabilizer to engage the instrument, the lower plate stabilizer beingconfigured to rest on the base and including at least one flexibleopening sized and shaped to at least partially surround the instrumentwhen normally relaxed and to immobilize the instrument when compressedinwardly toward the instrument; and an upper plate that is relativelymore rigid than the resilient lower plate stabilizer, configured to reston the resilient lower plate, and comprising a feature complementary tothe normally relaxed size and shape of each flexible opening of theresilient lower plate stabilizer, yet shaped and sized to compress eachsuch flexible opening inwardly upon compression of the upper plate andlower plate together.
 92. A device for immobilizing a primaryinstrument, including: a base; attachable to the base, a resilientdetachable C-shaped stabilizer to engage the instrument, the C-shapedstabilizer being configured to rest on the base and defining a flexiblewedge-shaped angular opening sized and shaped to immobilize theinstrument when normally relaxed yet release the instrument whenexpanded circumferentially away from the instrument; and attachable tothe wedge-shaped opening of the C-shaped stabilizer, a separate spreaderthat includes a pair of surfaces angularly spaced from each other by anamount greater than the amount of the flexible wedge-shaped angularopening of the resilient C-shaped stabilizer when normally relaxed. 93.An access device including: a mounting unit having a mounting plane; aprimary guide assembly that defines at least one insertion axis; arotating joint, attaching the guide assembly to the support structure,the rotating joint allowing rotation of the primary guide structureabout a rotation axis normal to the mounting plane; a first lockingdevice that fixes an orientation of the rotating joint; an arcuatesliding joint, attaching the guide assembly to the support structure,the arcuate sliding joint capable of adjusting an insertion angle of atleast one insertion axis with respect to the rotation axis, the rotationaxis and the insertion angle intersecting at the common point of theinsertion angle at the mounting plane; a second locking device,associated with the arcuate sliding joint, that fixes the insertionangle within a range of motion; a ball and socket joint, coupled to thearcuate sliding joint, allowing further adjustment of the insertionangle; and a third locking device that fixes the ball and socket jointwithin a range of motion.
 94. The access device of claim 93, in whichthe primary guide assembly is detachable from the ball-and-socket joint,a portion of the primary guide assembly fitting within a ball of theball-and-socket joint using a tapered outside surface so that theprimary guide assembly is held in the ball by a wedge formed by thetapered outside surface.
 95. The access device of claim 93, in which theball-and-socket joint further includes a plurality of ball adjustmentcontacts, each ball adjustment contact being adjustable with respect toa socket of the ball-and-socket joint, and each ball adjustment contactbeing in communication with the ball.
 96. The access device of claim 95,in which the plurality of ball adjustment contacts include threadedmembers that are threaded through the socket, and contact the ball. 97.The access device of claim 93, further including a reference devicecoupled to the primary guide assembly wherein the reference devicelocates at least one of the insertion axes.
 98. The access device ofclaim 97, in which the reference device includes a number of lightemitting diodes.
 99. The access device of claim 97, in which thereference device includes a number of light reflectors.
 100. The accessdevice of claim 97, in which the reference device includes one or moreelectrical coils.
 101. The access device of claim 93, in which the atleast one insertion axis includes a central insertion axis and aperipheral insertion axis.
 102. The access device of claim 93, in whichthe at least one insertion axis includes a central insertion axis andfour peripheral insertion axes.
 103. The access device of claim 93,further including a secondary guide device, having a secondary insertionaxis, the secondary guide device being coupled to the primary guideassembly.
 104. The access device of claim 103, in which the secondaryinsertion axis is collinear with the central insertion axis.
 105. Theaccess device of claim 103, in which the secondary insertion axis iscollinear with one of the peripheral insertion axes.
 106. The accessdevice of claim 93, further including an alignment device coupled to theprimary guide assembly, a portion of the alignment device being visibleusing an imaging device.
 107. The access device of claim 106, in whichthe alignment device includes a fluid filled stem that is visible usingmagnetic resonance imaging (MRI).
 108. The access device of claim 106,further including a processor that indicates when the insertion axis isaligned with a target within a patient.
 109. The access device of claim93, further including at least one sheath adapted for insertion throughthe primary guide assembly.
 110. The access device of claim 109, furtherincluding at least one stylet adapted for insertion through the at leastone sheath.
 111. The access device of claim 110, in which the sheathcovers a first longitudinal portion of the stylet, leaving a secondlongitudinal portion of the stylet exposed.
 112. The access device ofclaim 109, in which the sheath includes a peel-away portion.
 113. Theaccess device of claim 109, in which the sheath includes: a first sheathportion; and a second sheath portion capable of rotating with respect tothe first sheath portion such that when rotated from a first position toa second position a longitudinal sheath opening is exposed.
 114. Theaccess device of claim 93, further including a device introducer thatcontrollably moves a primary device along the insertion axis.
 115. Theaccess device of claim 114, in which the device introducer includes alocally mounted indicator device that is capable of locating a positionof a primary medical device along the insertion axis.
 116. The accessdevice of claim 115, in which the locally mounted indicator deviceincludes at least one of a linear encoder and a potentiometer.
 117. Theaccess device of claim 93, further including a fixing device coupled tothe mounting unit, the fixing device being capable of fixing thelocation of a primary device along the insertion axis.
 118. The accessdevice of claim 117, wherein the fixing device includes: a body, thebody having an opening with a first surface; a fixing unit, the fixingunit having a second surface that is adjustable with respect to thefirst surface; and a locking device capable of holding the fixing unitin a position with respect to the body such that the first and secondsurfaces engage the primary medical device, fixing it in a locationalong the insertion axis.
 119. The access device of claim 118, furtherincluding a cap that is capable of substantially covering an insertionopening in the mounting unit.
 120. The access device of claim 119,further including a groove that allows a primary device to remain fixedin a location along the insertion axis, while the insertion opening iscovered with the cap.
 121. The access device of claim 93, furtherincluding a removable centering device, the removable centering deviceincluding: a centering body; a number of insertion opening contactscoupled to the centering body; and an attachment device that isremovably coupled to the mounting unit during a mounting procedure. 122.The access device of claim 93, further including a pivot joint,attaching the guide assembly to the support structure, the pivot jointcapable of adjusting a first insertion angle of at least one insertionaxis with respect to a first direction in the mounting plane.
 123. Amethod including: securing a base portion of a guide lumen carryingassembly around an entry portal in a surface; rotating at least aportion of the guide lumen carrying assembly about a first axis that issubstantially concentric to the entry portal and substantiallyorthogonal to the surface; tilting at least a portion of the assembly sothat a second axis, extending concentrically through the guide lumen, isat a desired angle with the first axis, the first and second axesmeeting at the entry portal in the surface; and fixing a position of theguide lumen, including securing the rotating portion of the guide-lumenassembly and securing the tilting portion of the guide-lumen carryingassembly.
 124. The method of claim 123, further including sphericallyadjusting a portion of the guide-lumen carrying assembly to orient atrajectory provided by the second axis in a desired direction withrespect to the entry portal, and wherein the fixing the position of theguide lumen further includes securing the spherically adjustable portionof the guide lumen carrying assembly.
 125. The method of claim 124, inwhich spherically adjusting includes adjusting an orientation of a ballhoused in a socket.
 126. The method of claim 125, in which sphericallyadjusting includes moving a position of the ball within the socket usingat least one threaded member engaging the ball.
 127. The method of claim123, further including introducing an instrument through the guide lumenand the portal substantially along a trajectory provided by the secondaxis.
 128. The method of claim 127, in which introducing the instrumentincludes introducing at least one instrument selected from the groupconsisting essentially of a sheath, a stylet, a guide, a primaryinstrument, and an electrode.
 129. The method of claim 127, in whichintroducing the instrument includes: coupling a sliding clamp to aportion of the guide-lumen carrying assembly; clamping a portion of theinstrument to the clamp; and advancing the sliding clamp toward theentry portal.
 130. The method of claim 127, in which introducing theinstrument includes: inserting a stylet into a lumen of a sheath; andadvancing the stylet and sheath through the guide lumen and the entryportal.
 131. The method of claim 130, further including removing thestylet from the lumen of the sheath.
 132. The method of claim 131,further including inserting an electrode into the lumen of the sheathand through the guide-lumen and through the entry portal.
 133. Themethod of claim 132, further including retracting the sheath from theentry portal by peeling the sheath into more than one piece.
 134. Themethod of claim 132, further including adjusting a distance by which thesheath extends into the entry portal by viewing an indicator on thesheath.
 135. The method of claim 123, further including receiving, intothe guide-lumen, a portion of an imagable device.
 136. The method ofclaim 135, in which receiving the portion of the imagable deviceincludes receiving an imagable device selected from the group consistingessentially of an MRI-imagable alignment stem, a CT-imagable alignmentstem, and a frameless navigation instrument.
 137. The method of claim135, in which the rotating and tilting are performed in conjunction withreal-time viewing of the imagable device, using a corresponding imagingmodality, to align a trajectory of the second axis with a targetlocation located through the entry portal beyond the surface.
 138. Themethod of claim 123, further including: securing a base access plate tothe surface around the entry portal; introducing an instrument throughthe entry portal to a target location beyond the surface; and securingthe introduced instrument to the base access plate.
 139. The method ofclaim 138, further including concentrically aligning the base accessplate to the entry portal.
 140. The method of claim 139, in which thealigning includes: inserting a screw-carrying positioner through anopening in the base access plate and into the entry portal to positionthe base access plate concentrically around the entry portal; screwingthe base access plate to the surface, thereby releasing the screws fromthe screw-carrying positioner; and removing the positioner.
 141. Themethod of claim 138, in which securing the introduced instrumentincludes clamping the introduced instrument.
 142. The method of claim138, further including laterally exiting the instrument from the baseplate.
 143. The method of claim 123, further including capping the entryportal.
 144. The method of claim 123, further including introducing aninstrument through the guide lumen and the entry portal toward a targetlocation beyond the surface of the entry portal.
 145. The method ofclaim 144, in which the guide lumen is a first guide lumen, and furtherincluding reintroducing the instrument through a second guide lumenoffset from the first guide lumen by a predetermined distance.
 146. Themethod of claim 123, in which the guide lumen carrying assembly providesa plurality of guide lumens, and further including selecting aparticular one of the guide lumens for introducing an instrument by atleast one of orienting and coupling a guide lumen selector to the guidelumen carrying assembly.